The human body’s immune system is its best defence against disease. It is also needed to help the body recover from illness and injuries. It is important to note that there are a variety of factors that result in a compromised immune system and the first step to facing these potential problems is to identify them. The major factors that can weaken the immune system include stress, bad eating habits, chronic disease, poor sleep hygiene, and unhealthy lifestyle habits.

How much of an impact does a person’s diet have on their immune system?

Malnutrition causes a decline in immune function and increases susceptibility to infection. Likewise, a vitamin or mineral deficiency can alter immune responses and suppress immune system function. Therefore, eating the right foods and getting the proper nutrition are the keys to a healthy immune system.

Also, people forget that it’s not just what we eat but how much. Athletes in particular, if they do not meet their energy requirements through their diet, their body responds by increasing stress hormone levels that have direct connections to lowered immune function. Fueling appropriately for your training is also essential for a healthy immune system. Carbohydrates are critical for fueling immune cells, so the most effective strategy for athletes to maintain immune function is to consume carbohydrates during exercise (depending on intensity and duration). Protein is also needed to synthesise key immune factors and to build and repair body tissues.

Finally, it is well studied that over seventy percent of your immune function arises from the healthy bacteria of your gut. A healthy gut is the result of a balanced diet, including consuming pre- and probiotic foods and it is these ‘good bacteria’ which help to restore the balance in your gut and prime your immune system to defend itself against pathogenic organisms.

What foods may weaken the immune system?

Avoid any foods that cause or increase inflammation in the body. These include:

  • Fried foods – e.g. chips, fries, pastries etc. These foods are high in triglycerides and saturated fat, which causes inflammation and a build-up of free radicals in the body.
  • Added sugars – a high consumption of added sugars can reduce the function of our body’s white blood cells, affecting their ability to fight off infections and as a result suppresses our immune system. Examples include lollies, soft drink, pastries, cereals, jams, syrups, commercially baked goods such as biscuits, cookies and muffins.
  • Refined grains and carbohydrates – these include white flour, breads, cereals and some pastas. This is mainly due to their low level of fibre. Fibre plays an important role in strengthening your immune system.
  • High consumption of red meat – Fatty red meat is high in saturated fat and if over-cooked/charred, it can result in free radical production. Choose lean cuts and opt for medium-rare when cooking, if you choose to consume red meat.

What foods can help to boost immunity?

While no single food will boost your immune system, poor nutrition can have a negative effect on the immune system. Therefore, it’s important to look at what specific vitamins, minerals, antioxidants and phytochemicals are essential for an optimal immune system and make sure you are consuming a variety of those foods on a regular basis.

  • Vitamin C – leafy green vegetables, citrus fruits, capsicum, chilli, berries, parsley
  • Vitamin E – Nuts and seeds, spinach, broccoli, dark leafy greens, avocado, trout, prawns, olive oil
  • Vitamin B6 – banana, chicken, tuna, salmon, chickpeas
  • Vitamin A – carrots, sweet potato, pumpkin, dark leafy greens, dried apricots, rock melon
  • Vitamin D – fatty fish (salmon, mackerel, sardines, tuna), mushrooms, fortified, milks
  • Selenium – nuts and seeds (especially Brazil nuts), sardines, tuna, wholemeal bread, pork, chicken, rye
  • Zinc – oysters, beef, lamb, spinach, nuts and seeds, raw cocoa, pork, chicken, chickpeas, mushrooms

Are there any vitamin/mineral supplements that can help to boost immunity?

If you planning on taking a supplement/s for the sole purpose of boosting your immune system, it’s important know which nutrients have been scientifically proven to do just that. Research has shown the below nutrients may be beneficial to supplement for some population groups. Whether they are taken as a multivitamin or separate supplements, it’s important to ask your health professional what is best for you:

  • Vitamin D – helps downregulate the inflammation response while upregulating antimicrobial proteins to assist in the defence in immune cells.
  • Glutathione – one of the body’s most important cellular defence against free radical damage and is a major antioxidant.
  • Glutamine – is the most abundant amino acid in the body and regulates immune cell activity. Glutathione supplementation helps boost glutamine levels.
  • Antioxidants – are important immune system boosters because of their ability to scavenge free radicals. Important antioxidants include:
  • Vitamin C – is a key factor of the immune system and prevents the production of free radicals as well as reduces DNA damage in immune cells. It also down regulates the production of pro-inflammatory proteins.
  • Vitamin E – is a powerful fat-soluble antioxidant, which protects cellular membranes of the immune system by trapping and blocking free radicals.
  • B vitamins – have an indirect contribution to antioxidant defence and deficiencies in this group of vitamins (especially B12 and B6) can cause abnormalities in immune response.
  • Lipoic acid – is a potent antioxidant with antiviral, immune-boosting and free radical-quenching activities. It helps to regenerate other antioxidants and raise glutathione levels.
  • Coenzyme Q10 – is a powerful antioxidant and free radical scavenger and plays an important role in the stimulation of the immune system and improves immune function.
  • Selenium – plays an important role in supporting normal antioxidant pathways. It also reduces the absorption and protects against heavy metals.
  • Zinc – is important for the maintenance of the immune system and deficiency in this mineral is linked to impaired immune function.
  • Probiotics -The gastrointestinal tract relies on live bacteria (microflora) to help support a healthy immune response. These probiotic bacteria help prevent foreign bacteria and allergens from passing through the intestinal wall and are important to the overall health of the immune system.
  • Green tea extract – the catechines found in green tea has potent antioxidant qualities and helps reduce free radical damage. Green tea extract is also high in vitamin C and B, which also helps in the inflammatory process and protects against cellular DNA damage.

Is exercise good for the immune system?

Similar to a healthy, balanced diet, exercise can contribute to general good health and therefore to a healthy immune system. It may contribute even more directly by promoting good circulation, thus improving cellular activity, which allows the cells of the immune system to move through the body freely and do their job more efficiently.

Exercising in moderation can help give the immune system a boost and it is thought that approximately twenty minutes of exercise a day is sufficient to take advantage of the benefits. The rationale behind this is that when a person exercises, the white blood cells, which combat bacteria and viruses, travel throughout the body faster and more efficiently. Also, exercise helps lowers the hormones that are released as a result of stress, which causes significant inflammation in the long-term. Elevated body temperature that results from exercise may also reduce the amount of bacterial growth.

Can too much exercise weaken the immune system?

As mentioned above, a healthy amount of exercise provides an overall “boost” to the immune system.However, over-training can have the opposite effect and reduce immune response and function. This is dependent on the type, duration and intensity of the exercise you perform. For example, endurance athletes (such as marathon runners, distance swimmers, and triathletes) have notably depressed immunity compared to other athletes, especially when it comes to upper respiratory tract infections. It has also been shown that when these elite athletes do get sick, their symptoms tend to last longer and be more severe.

Studies have shown that the kind of exercise that produces an immune-suppressed response includes:

  • Relatively long workouts (1.5 hours or more), especially without refuelling during and after the workout.
  • A reasonably high intensity, but not excessively difficult (since you have to be able to keep it up for a while).
  • An inadequate recovery/rest period between workouts.

The reason why a suppressed immune system can occur at this level may come down to the fact that exercise raises the levels of norepinephrine and cortisol, two “stress hormones” that tend to suppress the immune system. These hormonal changes of exercise then cause the numbers of immune cells to drop immediately during and after the workout.

Studies have also shown that exercise also decreases levels of the amino acid glutamine, which as mentioned above plays an important role in regulating immune cell activity.

If you are already sick, are there any foods that may help you get better faster?

There may be some foods that that help reduce the severity and duration of the common cold and flu. Taking into consideration all the important vitamins, minerals and antioxidants as mentioned previously, consuming foods that are jammed-packed with these is the best bet. My pick of foods to supercharge your immune system include:

  • Citrus fruits high in vitamin C – think lemon, oranges, limes, mandarins etc.
  • Papaya
  • Ginger
  • Garlic
  • Berries
  • Protein
  • Pineapple
  • Turmeric
  • Carrots
  • Bone broth

Further compounding the problem is that millions of doctors erroneously prescribe antibiotics to patients seeking relief for their cold symptoms. The inherent danger in this approach is that persistent misuse of antibiotics further weakens an already compromised immune system and may contribute to the development of antibiotic-resistant pathogens.

When the immune system functions optimally, people are less likely to be infected by the countless bacteria and viruses to which they are exposed each day. In fact, proper immune function is essential to mounting an antibody response to the flu vaccine, which conventional doctors recommend to elderly patients to help protect against common strains of the influenza virus.

Immune function may also be weakened by factors ranging from chronic stress and poor nutrition to previous illnesses. When the immune system is compromised, a simple cold can quickly progress to full-blown pneumonia.